docs: def clear_dtreat(self, force=False):
          """ Clear all treatment parameters in self.dtreat
  
          Subsequently also clear the working copy of data
          The working copy of data is thus reset to the reference data
          """
          lC = [self._dtreat[k] is not None for k in self._dtreat.keys()
                if k != 'order']
          if any(lC) and not force:
              msg = """BEWARE : You are about to delete the data treatment
                                i.e.: to clear self.dtreat (and also self.ddata)
                                Are you sure ?
                                If yes, use self.clear_dtreat(force=True)"""
              raise Exception(msg)
          dtreat = dict.fromkeys(self._get_keys_dtreat())
          self._dtreat = self._checkformat_inputs_dtreat(dtreat)
          self.clear_ddata()